In Alma 12:14, Alma presented one of the most important mysteries, realing how we will be judged:
For our words will condemn us, yea, all our works will condemn us; we shall not be found spotless; and our thoughts will also condemn us; and in this awful state we shall not dare to look up to our God; and we would fain be glad if we could command the rocks and the mountains to fall upon us to hide us from his presence. (12:14)
Just as students wonder what their final exam is going to be like, people are concerned about what the final judgement will be based on. As part of their basic doctrine, the Nephites believed that all men would be resurrected and would have to stand before God to be judged according to how they had lived. Alma went into more detail on the elements of that final judgment in this text than is available elsewhere. He taught that people would be judged on three elements, deeds, words, and thoughts.
The idea of being judged based on our deeds, or individual actions, is comfortable enough for most people, but how about our words? Are people prepared to be judged on their words? Jesus spoke of that same principle, "By whatsoever measure you mete." In other words, the judgments that people have themselves spoken will set the rules or the orders of judgment upon which they will be judged. This judgment of words is scary, for measuring one’s words is rather harder than controlling one’s deeds.
However, what about "our thoughts will also condemn us"? How many people are ready to be judged according to their thoughts? In this, there is nowhere to hide! That is the same principle that Jesus taught in the Sermon on the Mount, a teaching also found in biblical and ancient Jewish thought. Judgment is not only based on what one does, but what one thinketh “in the heart” (see Genesis 27:41; Psalms 14:1; Luke 2:25).
How can one repent of bad thoughts? How can one get those out of the mind? We must feel godly sorrow for our mental sins. Like Zeezrom, we must, to some extent, suffer spiritual migraines over our intellectual mistakes (see Alma 15:3, 5). In many ways, their effects on ourselves and on others are the hardest to undo, but through Jesus Christ’s Atonement, the human intellect can be transformed into an instrument for loving God. The Atonement, through repentance, is the only way that these things can be cleansed and changed. A change of heart can also lead to a change of mind. Alma 12:14 is a beautiful text. What Alma taught is priceless. These are the words by which we will be judged. These words will guide us unto eternal life.
John W. Welch, "And with All Thy Mind," BYU Speeches, September 30, 2003.